Heat sink

ABSTRACT

A heat sink including a main body and a plurality of porous structures is disclosed. The main body has a plurality of hollow fins and a base. The fins and the base form a closed room. The porous structures are set on the interior surfaces of different fins, and are connected to the base. Each porous structure defines a vapor chamber.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/007,192, filed Dec. 09, 2004, which claims priority to TaiwanApplication Serial Number 93106818, filed Mar. 15, 2004, the disclosureof which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVETION

a) Field of the Invention

The invention relates to a heat sink and, more particularly, to a heatsink that is able to dissipate heat quickly and efficiently.

b) Description of the Prior Art

With the advancement of electronic technology, the electronic componentsare miniaturized and densely packaged. However, this correspondinglyproduces more heat, and therefore relying on natural or forcedconvection is insufficient to remove heat.

The conventional method of removing heat generated from electroniccomponents is to conduct the heat from a heat source to a heat sink andthen to dissipate the heat to the surroundings through natural or forcedconvection to the fins of the heat sink. However, the conventional heatsinks with fins have some problems that do affect the efficiency of heatremoval. For instance, a deficiency in temperature gradient due to thetemperature difference between the fin surfaces and the heat sinkairflow being only 5-10 degrees Celsius; the heat resistance problemsdue to the material and structure of the heat sink and low finefficiency that is less than 70%. These problems are the root causes forthe conventional heat sinks not able to increase its' heat dissipationefficiency and further unable to remove the heat produced by electroniccomponents sufficiently.

Thus, U.S. Pat. No. 6,490,160 has disclosed a heat sink composed of avapor chamber in view of the aforementioned problems. The concept ofthis patent is to form a single vapor chamber in a heat sink, whereinthe top of the vapor chamber is composed of an array of sheet taperedhallow pins deeply mounted in the heat sink fins, and the bottom of thevapor chamber is a single chamber connected to the bottom of all sheettapered hollow pins. The heat sink according to this patent dissipatesheat by having a working fluid to absorb heat and to be vaporized to thehollow pins and then to be liquefied again after exchanging heat withthe outer surroundings. After the condensation, the working fluid(liquid) flows along the groove wick structure on the surface of thehollow pins and returns to the chamber from the outer wall.

Nonetheless, the path for the working fluid to return to the chamber islong. Therefore, under a large heat-loading situation, there may be nocondensed liquid (working fluid) in the vapor chamber and cause thechamber to dry out. In addition, the single phase state (only vapor) inthe heat conductive mechanism and the long return path can make the finsexcept the outmost fins ineffective. Under this condition, the effectivedissipating surface is greatly reduced and hence lowers theeffectiveness of the heat sink.

Moreover, another heat sink with vapor chamber has been disclosed in USpatent application serial number 2002/0118511. This patent applicationalso forms a single vapor chamber in the heat sink, the chamber bottomis still a single chamber connected to all hollow pin except that amatrix arrangement of the columnar hollow pins is applied. This patentapplication utilizes a working fluid to absorb heat in the chamber andto be vaporized to the hollow pins. The vaporized working fluid thenexchange heat with the surroundings and condenses, and then tricklesdown along the sidewall and back into the chamber due to gravity force.Since gravity is the return-flow mechanism used in this application,direction problems do exist. That is, when the installation direction ofthe heat sink changes, the return-flow mechanism becomes inoperable.

In regards to the foregoing statements, US patent application2002/0118511 also disclosed a method combining the two technologies byforming a porous structure inside the hollow fins, so that the workingfluid can return to the chamber through the porous structure bycapillary force. However, this technology did not solve the problem thatexists in the U.S. Pat. No. 6,490,160, where the dry out occurs and allbut the outmost hollow fins are inoperable under a high heat-loadingcondition, which lowers the dissipation efficiency.

SUMMARY OF THE INVENTION

To solve the abovementioned problems, the present invention discloses aheat sink with high heat dissipation efficiency under any heat loading.

An object of the invention is to provide a heat sink with high heatdissipation efficiency under high heat loadings.

Another object of the invention is to provide a heat sink with high heatdissipation efficiency when installed in any direction.

Yet another object of the invention is to provide a heat sink whichprevents dry outs and hot spots from occurring.

The invention discloses a heat sink including a main body and aplurality of porous structures. The main body has a plurality of hollowfins and a base, the fins and the base form a closed room. The porousstructures are set on the interior surfaces of a different fin and areconnected to the base, and each porous structure defines a vaporchamber.

The invention also discloses a heat sink including a main body and aplurality of porous structures with the main body having a plurality ofhollow protrusions and a base. The protrusions and the base form aclosed room. The porous structures are set on the interior surfaces of adifferent protrusion and are connected to the base, and each porousstructure defines a vapor chamber.

The porous structures are wick structures; common wick structuresinclude mesh, fiber, sintered, groove wicks, or combinations thereof.The porous structures and the main body are assembled by methods such assintering, adhering, filling, or depositing. The material of the porousstructures includes plastics, alloys or metals such as copper, aluminum,iron, porous non-metallic materials and mixtures thereof. The porousstructures contain a working fluid; the working fluid can be inorganiccompounds, water, alcohols, liquid metals such as mercury, ketones,refrigerants such as HFC-134a, other organic compounds or mixturesthereof.

The main body can be one-piece molded or composed of several components.The components are bind together by soldering, engaging, embedding,adhering, or combinations thereof. Neighboring vapor chambers arecommunicated with each other directly, or indirectly in fluidcommunication through the porous structures.

The vapor chambers are arranged in the closed room either in an arrayarrangement, a longitudinal arrangement, a parallel arrangement, or atransverse arrangement.

Since the heat sink according to the invention utilizes wick structures(porous structures) to form several small vapor chambers and/or smallsectors, the wick structure of every protrusion forms an independentheat-removal cycle. So, under high heat-loading situation, the dry outswill not occur and the high heat dissipation efficiency is maintained.

Moreover, since the bottom of the small vapor chambers and/or smallsectors are composed of connecting wicks (heat-absorptive portion), theworking fluid in each small vapor chamber are in fluid communication,and thus the possibility of hot spots occurring is lowered, and the heatis evenly distributed to each small vapor chamber and/or small sector.

Furthermore, since the return-flow mechanism of the heat sink accordingto the invention uses capillary force but not simply relies on gravity,the return-flow speed of the working fluid in the heat sink will not beaffected by the direction for installation.

The vapor chamber in the heat sink according to the invention iscomposed of a plurality of small vapor chambers and/or small sectors,and therefore the return-flow path of the working fluid is short, andthe return-flow speed and heat dissipation efficiency are enhanced.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a preferred embodiment of a heat sinkin accordance with the invention;

FIG. 2 is an enlarged partial view of the preferred embodiment of FIG.1; and

FIG. 3 illustrates the vapor flow in the preferred embodiment of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a heat sink 100 includes a main body 102 and aplurality of porous structures 110 inside the main body 102, wherein themain body 102 has a closed room 124 formed therein.

The main body 102 has a plurality of hollow protrusions 120 and a base122 connecting to a heat source 118. The shape and/or size of the base122 varies in accordance with the placement of the protrusions 120 andthe shape of the heat source 118. Each protrusion 120 is hollow and hastwo ends; the end proximate the base 122 has an opening and the otherend is closed. The protrusions 120 are in a shape of fin, column,lamella, cone, or lump; and in a form of curve, arch, slant, vertical,or any other form. The protrusions 120 and the base 122 of the main body102 can be one-piece molded or jointed by soldering, engaging,embedding, adhering, or a combination of any of the methods listedthereof. Moreover, the closed room 124 can be divided into a pluralityof vapor chambers 112 by the porous structures 110.

The porous structures 110 are embedded on the interior surfaces of themain body 102, and are sealed therein. The porous structures 110 form aplurality of vapor chambers 112 in the main body 102. Each porousstructure 110 is sectioned into a conductive portion 104 and aconnective portion 106, and a heat-absorptive portion 108. The porousstructures 110 are for absorbing working fluid; the condensed workingfluid flows through the conductive portion 104, the connective portion106, and into the heat-absorptive portion 108. The working fluid is ofinorganic compounds, water, alcohols, liquid metals such as mercury,ketones, refrigerants such as HFC-134a, other organic compounds, or amixture of any of the fluids listed thereof. Using the pressure in thevapor chambers 112 can control the boiling temperature of the workingfluid. The heat-absorptive portion 108 set on the interior surfaces ofthe base 122 is for absorbing the working fluid. The conductive portion104 set on the interior surfaces of the protrusion 120 is for conductingthe condensed working fluid to the heat-absorptive portion 108. Theother connective portion 106 is set between the heat-absorptive portion108 and the conductive portion 104, and connected to both portions.

The conductive portion 104, the connective portion 106 and theheat-absorptive portion 108 can be made of material such as copper,aluminum, iron, other metals and/or alloys, plastics, other porousnon-metallic materials, or a mixture of any of the materials listedthereof. The conductive portion 104, the connective portion 106 and theheat-absorptive portion 108 are required to have a porous formation suchas wicking structures. Common wicking structures include mesh wicks,fiber wicks, sintered wicks, groove wicks, or other structures includinga combination of any of the wicking structures listed thereof. Theporous structures 110 and the main body 102 are assembled by sintering,adhering, filling, or depositing.

The connective portion 106 106 is set between neighboring protrusions120 so that the working fluid in the conductive portion 104 can flowquickly to the heat-absorptive section 108 along the connective portion106. The connective portion 106 divides the closed room 124 into aplurality of vapor chambers 112; each vapor chamber 112 corresponds toat least one of the protrusions 120. The connective portion 106 can alsodivide the closed room 124 into a plurality of sectors; the sectors eachcorresponds to a protrusion 120 and the neighboring sectors arecommunicated with each other. The vapor chambers 112 or the smallsectors can be disposed in array, parallel, longitudinal, transverse,diagonal or irregular arrangements.

Although the closed room 124 has been divided into a plurality of vaporchambers 112 and/or small sectors by the connective portions 106, theworking fluid in the heat-absorptive portion 108 on the bottom of eachvapor chamber is in fluid communication with other vapor chambers. Thusthe occurred probability of the partial hot spots on the heat sink 100is reduced, and the heat is distributed evenly on the bottom of the heatsink 100.

The heat sink 100 described above is used to illustrate the heat-removalmechanism used in the invention. In this embodiment, the base 122 of theheat sink 100 is installed on the heat source 118, wherein the heatsource 118 is composed of a heat-generating element 116 and a conductingstructure 114 connected to the heat-generating element 116. Theconducting structure 114 can be a heat-dissipating paste, or aphase-changing metal sheet; the heat-generating element 116 can be acomputer-processing unit (CPU), or a semi-conductor chip. Forillustration purpose, the protrusions 120 exemplify a fin shape in thisembodiment.

When the bottom of the vapor chambers 112 is heated and the temperatureof the working fluid raises to the boiling point, the working fluid inthe heat-absorptive portions 108 boils and evaporates, causing thepressure in the vapor chambers 112 to rise and the vapors move towardsthe fins quickly. The heat in the fins is then dissipated by natural orforced convection; the vapors condensate into liquid on the interiorsurfaces of the fins and the working fluid (liquid) penetrates into theconductive portions 104 (wick structure) in the fins. Since theheat-absorptive portions 108 (wick structure) are drier than theconductive portions 104, the capillary force drives the working fluid(liquid) to flow back to the bottom of the vapor chambers 112 and hencea heat-removal cycle is completed.

Since the bottom edges of the fins are connected to the base 122 withthe connective portions 106 (wick structure), the return-flow speed ofthe working fluid is enhanced and dry out is prevented from occurring.

Referring to FIG. 2, the section “A” of the partial view of theconnective portion 106 is enlarged to show the detailed structurethereof. The connective portion 106 further includes a plurality ofholes 210 thereon for evenly distributing the vaporized fluid in thevapor chambers 112. Therefore, the vaporized fluid in the vapor chambers112 can quickly and uniformly distribute in the vapor chambers 112.

Referring to FIG. 3, the vapor can easily flow to the adjacent vaporchambers 112 along the arrow signs 312 and to the protrusion 120 alongthe arrow signs 310.

Concluding from the description above, the heat sink according to theinvention utilizes wick structures (porous structures) to form aplurality of small vapor chambers and/or small sectors, so that the wickstructure in each protrusion forms an independent heat-removal cycle.Thus even under high heat-loading situations, dry outs caused by thelack of working fluid will not occur and the heat-dissipating effect canbe maintained. In addition, the connective portions include a pluralityof holes so that the vapor in the vapor chambers is uniformlydistributed. Hence, the heat can be more smoothly distributing in theheat sink.

Moreover, the bottom of the small vapor chambers and/or small sectorsare made of connecting wick structures (heat-absorptive portions),thereby the working fluid in each small vapor chamber and/or smallsector is in fluid communication via the wick structures on the bottom.This in turn lowers the occurred probability of hot spots and the heatis evenly distributed to each small vapor chamber and/or small sector.

Furthermore, since the heat sink according to the invention utilizescapillary force in the return-flow mechanism instead of simply relyingon gravity, thus the installation direction of the heat sink will notaffect the return-flow speed.

In addition, since the vapor chamber of the heat sink according to theinvention includes a plurality of small vapor chambers and/or smallsectors, each small vapor chamber and/or small sector has shorterreturn-flow path than that of the conventional technology. Therefore,the return-flow speed of the working fluid is increased and theheat-dissipating effect is enhanced.

While the invention has been described by way of example and in terms ofthe preferred embodiment, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements aswould be apparent to those skilled in the art. Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A heat sink, comprising: a main body having a plurality of hollowfins and a base, each fin having a close end and an open end facing thebase, and the fins and the base forming a closed room; and a pluralityof porous structures comprising a plurality of conductive portions,connective portions and heat-absorptive portions, wherein the conductiveportions are continuously formed on the interior surfaces of the hollowfins, the heat-absorptive portions are formed on the base, and eachconnective portion is set between the neighboring conductive portionsand connected to the heat-absorptive portions on the base to divide theclosed room into a plurality of vapor chambers, and each connectiveportion comprises a plurality of holes for allowing vaporized fluid topass therethrough.
 2. The heat sink as described in claim 1, wherein theporous structures are wicks selected from the group consisting of acombination of one or more of mesh wicks, fiber wicks, sintered wicks,and groove wicks.
 3. The heat sink as described in claim 1, wherein theporous structures contain a fluid selected from the group consisting ofa mixture of one or more of inorganic compounds, water, alcohols, liquidmetals, ketones, refrigerants, and organic compounds.
 4. The heat sinkas described in claim 1, wherein the material of the porous structuresis selected from the group consisting of a mixture of one or more ofplastics, metals, alloys, and porous non-metal materials.
 5. The heatsink as described in claim 1, wherein the fins and the base are formedby a method selected from the group consisting of a combination of oneor more of soldering, engaging, embedding and adhering, or the main bodyis one-piece molded.
 6. The heat sink as described in claim 1, whereinthe fins are arranged in a longitudinal, parallel, transverse, diagonal,or irregular array.
 7. The heat sink as described in claim 1, whereinneighboring vapor chambers are communicated with each other or in fluidcommunication through the porous structures.
 8. A heat dissipatingdevice, comprising: a main body having a plurality of hollow protrusionsand a base, each protrusion having a close end and an open end facingthe base, and the protrusions and the base forming a closed room; and aplurality of porous structures comprising a plurality of conductiveportions, connective portions and heat-absorptive portions, wherein theconductive portions are continuously formed on the interior surfaces ofthe hollow protrusions, the heat-absorptive portions are formed on thebase, and each connective portion is set between the neighboringconductive portions and connected to the heat-absorptive portions on thebase to divide the closed room into a plurality of vapor chambers, andeach connective portion comprises a plurality of holes for allowingvaporized fluid to pass therethrough.
 9. The heat dissipating device asdescribed in claim 8, wherein one of the protrusions has a fin shape,columnar shape, lamellar shape, conical shape, or lump shape.
 10. Theheat dissipating device as described in claim 8, wherein the porousstructures are wicks.
 11. The heat dissipating device as described inclaim 10, wherein the wicks are selected from the group consisting of acombination of one or more of mesh wicks, fiber wicks, sintered wicks,and groove wicks.
 12. The heat dissipating device as described in claim8, wherein the porous structures and the main body are assembled bysintering, adhering, filling, or depositing.
 13. The heat dissipatingdevice as described in claim 8, wherein the porous structures contain afluid selected from the group consisting of a mixture of one or more ofinorganic compounds, water, alcohols, liquid metals, ketones,refrigerants, and organic compounds.
 14. The heat dissipating device asdescribed in claim 8, wherein the material of the porous structures isselected from the group consisting of a mixture of one or more ofplastics, metals, alloys, and porous non-metal materials.
 15. The heatdissipating device as described in claim 8, wherein the protrusions andthe base are formed by soldering, engaging, embedding or adhering, orthe main body is one-piece molded.
 16. The heat dissipating device asdescribed in claim 8, wherein neighboring vapor chambers arecommunicated with each other, or in fluid communication through theporous structures.
 17. The heat dissipating device as described in claim8, wherein the vapor chambers of the porous structures are arranged inthe closed room in a longitudinal, parallel, transverse, diagonal, orirregular array.
 18. A heat sink, comprising: a main body having aplurality of hollow fins and a base, the fins and the base forming aclosed room; and a plurality of porous structures continuously formed onthe interior surfaces of the hollow fins and connected to the base,wherein the porous structures further comprise a plurality of connectiveportions, each connective portion is set between the porous structureson neighboring hollow fins and connected to the porous structures on thebase to divide the closed room into a plurality of vapor chambers, andeach connective portion comprises a plurality of holes for allowingvaporized fluid to pass therethrough.